Enter both values to calculate milliamp hours
Watt Hours (Wh)
Volts (V)
Common:
Milliamp Hours (mAh)
Result will appear here
Understanding Power Bank Capacity
Power bank capacity can be measured in mAh or Wh:
- Energy (Wh) = Capacity (mAh) × Voltage (V) ÷ 1000
- Capacity (mAh) = Energy (Wh) × 1000 ÷ Voltage (V)
For USB and Portable Power
Understanding these relationships helps you:
- Compare power banks - Use Wh for accurate comparison
- Airlines allow 100Wh - Know if your power bank is carry-on safe
- Calculate charges - How many phone charges you'll get
- Size solar chargers - Match panel to power bank capacity
Real-World Solar Examples
Tesla Powerwall in mAh
A 13,500Wh Powerwall at ~50V = 270,000 mAh. That is equivalent to 13.5 typical 20,000 mAh power banks — highlighting the scale difference between portable and home energy storage.
Small Solar Battery as a Power Bank
A 12V 7Ah sealed lead-acid battery (84Wh) converts to 16,800 mAh at 5V USB output. Roughly equal to a 20,000 mAh power bank, but weighs 5 lbs vs 12 oz.
Portable Solar Generator USB Capacity
A 500Wh power station at 5V USB = 100,000 mAh. At USB-C PD 20V = only 25,000 mAh. The same battery has drastically different mAh numbers depending on output voltage.
When You'll Need This Conversion
- Comparing Solar Generator to Power Banks — A 300Wh portable power station at 5V = 60,000 mAh equivalent — equal to three 20,000 mAh banks. But the power station also provides 12V DC and 120V AC, making it more versatile for solar charging.
- Phone Charges from a Small Solar Battery — A 12V 20Ah solar battery (240Wh) converts to 48,000 mAh at 5V. Each smartphone needs ~19Wh per charge, yielding about 10 charges after conversion losses.
- Solar USB Charging Station for Events — Charging 50 phones (950Wh total) = 190,000 mAh at 5V. Choose between ten 20,000 mAh power banks (pre-charged) or a 1,000Wh power station with a 200W solar panel for continuous replenishment.
Solar Tips & Common Mistakes
Always Specify Voltage with mAh: "100,000 mAh" is meaningless without voltage. At 3.7V = 370Wh; at 5V = 500Wh; at 12V = 1,200Wh. Some cheap solar generators inflate mAh by using low voltage. Always check the Wh rating instead.
USB Conversion Losses Reduce Effective mAh: A 12V battery outputting through a USB converter at 5V loses 10–20% as heat. A 1,200Wh battery theoretically = 240,000 mAh at 5V, but realistically yields 192,000–216,000 mAh.
USB-PD Voltage Changes the Math: A laptop charging at 20V PD draws far fewer mAh than a phone at 5V for the same energy. Think in Wh, not mAh, for mixed-device charging stations.
Solar Calculators
Related Conversion Calculators
Last updated: January 5, 2026
